A rotation angle detection apparatus according to a related art detects a rotation angle by detecting a rotating magnetic field. For example, JP 5126325 B2 discloses a rotation angle detection apparatus which calculates a rotation angle by using at least four output signals outputted from midpoints of half bridges.
An output value from a half-bridge circuit includes an offset displacement, and the rotation angle detection apparatus disclosed in JP 5126325 B2 performs offset correction in a controller. However, different from a case where output values from full-bridge circuits are used, an offset cannot be cancelled completely when affected by a phase difference caused by a manufacturing error, interconnect resistance, temperature characteristics, and the like. Also, in the event of an abnormality is occurred in partial output signals, an angle calculation is continued by using sine signals or cosine signals outputted from a single half bridge. In this case, an offset cannot be cancelled completely. Hence, detection accuracy may possibly be deteriorated in comparison with detection accuracy in a properly operating state.